HP StorageWorks Scalable File Share - Manual (Page 121)

Managing quotas 5–37
5.7 Managing quotas
Quotas allow you to control how many blocks or inodes a user or group can use in a file system. In this
release of the HP SFS software, only hard limits are supported.
Quotas are managed on both the HP SFS system and on a client system. You can manage the client portion
of the quotas functionality on any HP SFS client system that has mounted the file system that is being
configured to use quotas.
Section 5.7.1 describes how quota tuning works on Lustre file systems. Section 5.7.2 provides instructions
for configuring quotas on individual file systems.
5.7.1 Understanding quota tuning
The granularity of quota operations on Lustre file systems can be tuned. It defaults to rather coarse
granularity settings that provide a good balance and trade-off between quota management overheads and
the distribution of available quota allocation among a number of backing OST devices.
Table 5-1 describes the options that are used to define the quota settings and shows their default values.
In general, Lustre reserves a unit of quota (block or file) to a device (OST or MDS) in each of the following
situations:
• The device has no quota reservation available.
• The unused portion of the existing reservation drops below a defined threshold.
For example, consider the case where the unit of block reservation is 100MB (the default) and the unused
quota threshold is 50% (the default).
The first time a user accesses an OST device, 100MB of the user’s quota is assigned to that OST device.
Table 5-1 Quotas options
Quota option Description
quotaon
This option has one of the following values:
•
u
— enables user quotas
•
g
— enables group quotas
•
ug
— enables both user and group quotas
iunit, bunit, itune, btune
These options control the quota settings in the file system. HP recommends that
you do not change the default values of these options.
• The
iunit
option specifies the size of the quota unit (that is, the number of
inodes) to be allocated to the user or group from the MDS device. The
default value is
5000
.
• The
bunit
option specifies (in MB) the size of the quota unit (that is, the
block size) to be allocated to the user or group from each OST device being
accessed. The default value is
100
(MB).
• The
itune
option specifies the unused quota threshold for inodes on MDS
devices; the value is interpreted as a percentage. One unit from the device
is allocated to the user or group when the free amount drops below this
percentage, and one unit is released from the user or group when the free
amount exceeds the amount of the unit plus this percentage. The default
value is
50
(%).
• The
btune
option specifies the unused quota threshold for blocks on OST
devices; the value is interpreted as a percentage. One unit from the device
is allocated to the user or group when the free amount drops below this
percentage, and one unit is released from the user or group when the free
amount exceeds the amount of the unit plus this percentage. The default
value is
50
(%).